Copywright The Marble Institute of America
Care and Cleaning for Natural Stone Surfaces
Granite is a virtually maintenance free material that requires little to no precautions. Oil or grease left to seep into the stone is granite’s biggest foe, and this is only if the granite is un-sealed or if the oil or grease is left to seep into the stone and dry overnight or for an extended period of time. If your sealed granite does darken because of oil or grease, a poultice can be made to draw the stain back out.
Care & Precautions
Use coasters under all glasses, particularly those containing alcohol and citrus juices. Many common foods and drinks contain acids that will dull or etch the surface of many stones.
Do not place hot items directly on the stone surface. Use trivets or mats under hot dishes and placemats under china, ceramics, silver or other objects that may scratch the surface.
Cleaning Procedures & Recommendations
Dust mop interior floors frequently using a clean non-treated dry dust mop. Sand, dirt and grit do the most damage to natural stone surfaces due to their abrasiveness. Mats or area rugs inside and outside an entrance will help to minimize the sand, dirt and grit that will scratch the stone floor. Be sure that the underside of the mat or rug is a non-slip surface. Normally, it will take the average person about eight to ten steps on a floor surface to remove sand or dirt from the bottom of their shoes.
Do not use vacuum cleaners that are worn. The metal or plastic attachments or the wheels may scratch the surface.
Clean stone surfaces with a few drops of neutral cleaner, stone cleaner or a mild dishwashing detergent and warm water. Use a clean rag mop on floors and a soft cloth for other surfaces for best results. Too much cleaner or soap may leave a film and cause streaks. Do not use products that contain lemon, vinegar, or other acids on marble or other calcareous stones. Rinse the surface thoroughly after washing with the soap solution and dry with a soft cloth. Change the rinse water frequently. Do not use scouring powders or creams; these products contain abrasives that may scratch the stone.
Bath and Other Wet Areas
In the bath or other wet areas, soap scum can be minimized by using a squeegee after each use. To remove soap scum, use a non-acidic soap scum remover or a solution of ammonia and water (about 1&Mac218;2 cup ammonia to 1 gallon water). Frequent or over use of ammonia solution may eventually dull the surface of the stone.
Outside Pool or Patio Areas
In outdoor pool, patio and hot tub areas, flush with clear water and use mild bleach solution to remove algae or moss.
Know Your Stone
Natural stone can be classified into two general categories according to its composition: siliceous stone or calcareous stone. Knowing the difference is critical when selecting cleaning products.
Siliceous stone is composed mainly of silica or quartz-like particles. It tends to be very durable and relatively easy to clean with mild acidic cleaning solutions. Types of siliceous stones include granite, slate, sandstone, quartzite, brownstone and bluestone.
Calcareous stone is composed mainly of calcium carbonate. It is sensitive to acidic cleaning products and frequently requires different cleaning procedures than siliceous stone. Types of calcareous stones include marble, travertine, limestone and onyx. What may work on siliceous stone may not be suitable on calcareous surfaces.
How to Tell the Difference
A simple acid sensitivity test can be performed to determine whether a stone is calcareous or siliceous. You will need a few drops of vinegar and an eyedropper. Because this test may permanently etch the stone, select an out of the way area and several inches away from a mortar joint. Apply a few drops of the vinegar to the stone surface about the size of a quarter. If the stone is calcareous, the vinegar will etch the stone. If little or no reaction occurs, the stone can be considered siliceous. Rinse the area thoroughly with clean water and wipe dry.
A polished finished on the stone has a glossy surface that reflects light and emphasizes the color and marking of the material.
A honed finish is a satin smooth surface with relatively little light reflection.
A flamed finish is a rough textured surface.
Spills and Stains
Blot the spill with a paper towel immediately. Don’t wipe the area, it will spread the spill. Flush the area with plain water and mild soap and rinse several times. Dry the area thoroughly with a soft cloth. Repeat if necessary. If the stain remains, you may try to remove the stain.
Identifying the type of stain on the stain surface is the key to removing it. If you don’t know what caused the stain, play detective. Where is the stain located? Is it near a plant, a food service area, an area where cosmetics are used? What color is it? What is the shape or pattern? What goes on in the area around the stain?
Surface stains can often be removed by cleaning with an appropriate cleaning product or household chemical. Deep-seated or stubborn stains may require the use of a poultice, or if needed, having your stone re-surfaced.
The following sections describe the types of stains that you may have to deal with and appropriate household chemicals to use and how to prepare and apply a poultice to remove the stain.
Types of Stains and First Step Cleaning Actions
Oil Based (grease, tar, cooking oil, milk, cosmetics)
An oil based stain will darken the stone and normally must be chemically dissolved so the source of the stain can be flushed or rinsed away. Clean gently with a soft, liquid cleanser with bleach OR household detergent OR mineral spirits OR acetone. A poultice may also be used. See below under Making and Using a Poultice for a recipe.
Organic (coffee, tea, fruit, tobacco, paper, food, urine, leaves, bark, bird droppings)
An organic stain may cause a pinkish-brown stain and may disappear after the source of the stain has been removed. Outdoors, with the sources removed, normal sun and rain action will generally bleach out the stains. Indoors, clean with 12% hydrogen peroxide (hair-bleaching strength) and a few drops of ammonia.
Metal (iron, rust, copper, bronze)
Iron or rust stains are orange to brown in color and follow the shape of the staining object such as nails, bolts, screws, cans, flower pots, metal furniture. Copper and bronze stains appear as green or muddy brown and result from the action of moisture on nearby or embedded bronze, copper or brass items. Metal stains must be removed with a poultice. (See section below for making and using a poultice). Deep-seated, rusty stains are extremely difficult to remove and the stone may be permanently stained.
Biological (algae, mildew, lichens, moss, fungi)
Clean with diluted ammonia OR bleach OR hydrogen peroxide (1/2 cup per gallon of water). DO NOT MIX BLEACH AND AMMONIA! THIS COMBINATION CREATES A LETHAL AND TOXIC GAS!
Ink (magic marker, pen, ink)
Clean with bleach or hydrogen peroxide (light colored stone only!) or lacquer thinner or acetone (dark colored stone only!)
Small amounts can be removed with lacquer thinner or scraped off carefully with a razor blade. Heavy paint coverage should be removed with a commercial “heavy liquid” stripper available from hardware stores or paint centers. Do not use acids or flame tools to strip paint from stone. Paint strippers can etch the surface of the stone; re-polishing may be necessary. Follow the manufacturer’s directions for use of these products, taking care to flush the area thoroughly with clean water. Protect yourself with rubber gloves and eye protection, and work in a well ventilated area. Use only wood or plastic scrapers for removing the sludge and curdled paint. Normally, latex and acrylic paints will not cause staining. Oil-based paints, linseed oil, putty, caulks and sealants may cause oily stains.
Water Spots and Rings (surface accumulation of hard water)
Buff with dry 0000 steel wool.
Fire and Smoke Damage
Older stones and smoke or firestained fireplaces may require a thorough cleaning to restore their original appearance. Commercially available “smoke removers” may save time and effort.
Etch Marks are caused by acids left on the surface of the stone. Some materials will etch the finish but not leave a stain. Others will both etch the surface and leave a stain. Once the stain has been removed, wet the surface with clear water and sprinkle on marble polishing powder (available from a hardware or lapidary store). Rub the powder onto the stone with a damp cloth or by using a buffing pad with a low speed power drill. Continue buffing until the etch mark disappears and the marble surface shines.
Efflorescence is a white powder that may appear on the surface of the stone. It is caused by water carrying mineral salts from below the surface of the stone rising through the stone and evaporating. When the water evaporates, it leaves the powdery substance. If the installation is new, dust mop or vacuum the powder. You may have to do this several times as the stone dries out. Do not use water to remove the powder; it will only temporarily disappear.
Scratches and Nicks
Slight surface scratches may be buffed with dry 0000 steel wool. Or, refer to the above sections on etch marks and follow the polishing procedure. Deeper scratches and nicks in the stone can be re-surfaced and re-polished in our shop.
Making and Using a Poultice
A poultice is a liquid cleaner or chemical mixed with a white absorbent material to form a paste about the consistency of peanut butter. The poultice is spread over the stained area to a thickness of about 1&Mac218;4 to 1&Mac218;2 inch with a wood or plastic spatula, covered with plastic wrap, taped down, and left to work for 24 to 48 hours. The liquid cleaner or chemical will draw out the stain into the absorbent material. Poultice procedures may have to be repeated to thoroughly remove a stain, and some stains may never be completely removed.
Poultice materials include kaolin, fuller’s earth, whiting, diatomaceous earth, powdered chalk, white molding plaster, flour, or talc. Approximately one pound of prepared poultice material will cover one square foot. Do not use whiting or iron-type clays such as fuller’s earth with acid chemicals. The reaction will cancel the effect of the poultice. A poultice can also be prepared using white cotton balls, white paper towels or gauze pads.
Cleaning Agents or Chemicals
Oil-based stains: Poultice with baking soda and water OR one of the powdered poultice materials and mineral spirits.
Organic Stains: Poultice with one of the powdered poultice materials and 12% hydrogen peroxide solution (hair bleaching strength) OR use acetone instead of the hydrogen peroxide.
Iron Stains: Poultice with diatomaceous earth and a commercially available rust remover. Rust stains are particularly difficult to remove.
Copper Stains: Poultice with one of the powdered poultice materials and ammonia. These stains are difficult to remove.
Biological Stains: Poultice with one of the poultice materials and diluted ammonia OR bleach OR hydrogen peroxide. DO NOT MIX BLEACH AND AMMONIA! THIS COMBINATION CREATES A LETHAL AND TOXIC GAS!
Applying and Using the Poultice
1. Prepare the poultice. If using powder, mix the cleaning agent or chemical to a thick paste the consistency of peanut butter. If using paper, soak in the chemical and let drain. Don’t let the paper drip.
2. Wet the stained area with distilled water.
3. Apply the poultice to the stained area about 1&Mac218;4 to 1&Mac218;2 inch thick and extend the poultice beyond the stain by 1 inch. Use a wood or plastic scraper to spread the poultice evenly.
4. Cover the poultice with plastic and tape the edges to seal it.
5. Allow the poultice to dry thoroughly, usually about 24 to 48 hours. The drying process is what pulls the stain out of the stone and into the poultice material. After about 24 hours, remove the plastic and allow the poultice to dry.
6. Remove the poultice from the stain, rinse with distilled water and buff dry with a soft cloth. Use the wood or plastic scraper if necessary.
7. Repeat the poultice application if the stain is not removed. It may take up to five applications for difficult stains.
8. If the surface is etched by the chemical, apply polishing powder and buff with burlap or felt buffing pad to restore the surface.
Do’s and Don’ts
* DO dust mop floors frequently
* DO clean surfaces with mild detergent or stone cleaner
* DO thoroughly rinse and dry the surface after cleaning with soap
* DO blot up spills immediately
* DO protect floor surfaces with non-slip mats or area rugs and counter tops surfaces with coasters, trivets or placements
* DON’T use vinegar, lemon juice or other cleaners containing acids on marble, limestone, travertine or onyx surfaces
* DON’T use cleaners that contain acid such as bathroom cleaners, grout cleaners or tub & tile cleaners
* DON’T use abrasive cleaners such as dry cleaners or soft cleansers
* DON’T mix bleach and ammonia; this combination creates a toxic and lethal gas.
* DON’T ever mix chemicals together unless directions specifically instruct you to do so.
This brochure has been reproduced with permission from The Marble Institute of America
Copyright 2003. All rights reserved. The Marble Institute of America